Liquid polysulfide and liquid polysulfide compositions are well known, having been described, for example in U.S. Pat. Nos. 3,331,782; 4,060,570; 3,852,214; 3,817,930; 3,770,678; 3,637,574; 3,518,211; 3,518,107; 3,349,047 and 2,466,936. Generally, liquid polysulfide polymers are materials having the structure HS(RSS--R'--SS).sub.x R"SH wherein R, R' and R" may be the same or different hydrocarbon, oxyhydrocarbon or thiahydrocarbon moieties. These polymers are generally linear, but may be branched, for example, by preparing these compositions with trichloropropane.
Liquid polysulfides are curable with a variety of oxidative curatives, particularly inorganic oxides and peroxides. Oxidative curatives link polysulfide polymers together by oxidation of terminal thio (--SH) groups to form disulfide (--S--S--) linkages. Examples of suitable curatives are given in U.S. Pat. No. 3,331,782, the teachings of which are incorporated herein by reference. Cured polysulfides in combination with various fillers, pigments, plasticizers etc. are useful, for example, as sealants and caulking materials. The molecular weights of polysulfides may vary over a wide range, e.g., from 500 to upwards of 25,000. Typically, high molecular weight polysulfides are produced, and then the molecular weight is adjusted downward by a split stripping process. This process also provides the free terminal thio moieties. Typically, commercial liquid polysulfides have molecular weights in the 1000 to 10,000 range.
As described in referenced U.S. Pat. No. 3,331,782, liquid polysulfides are generally provided in a two-package system with the polysulfide material separately packaged from the curative. The curative is typically provided as a paste that is added to the liquid polysulfide material at the time of use. The high reactivity of liquid polysulfides with the curative, particularly when the curative is a peroxide, has generally precluded these components from being packaged in a one-package system.
Two-package systems are inherently disadvantageous relative to one-package systems. The need to mix at the site of application is at least an inconvenience for the user. Inadequate or improper mixing may result in an unsatisfactory cured product. The lack of mixing apparatus and/or the inconvenience of mixing may cause a potential user to seek an alternative sealing or caulking material. It is therefor a general object of the present invention to provide a one-package composition containing both polysulfide and an oxidative curative therefor.
There have been produced one-package mixtures of polysulfides and inorganic curatives in which premature curing is prevented by complete removal of water from the system. This type of system relies of absorption of water vapor from the atmosphere for eventual curing. A major disadvantage of such a system is the inordinately long cure time. Typically, such a system requires at least about 24 hours to become tack-free and much longer to completely cure. Such extended cure times are unacceptable for many sealing and caulking applications.
It is also known to produce polysulfide latexes in which liquid polysulfides are emulsified in an aqueous medium. Such latexes are described, for example in U.S. Pat. No. 3,770,678. These latexes do not contain an oxidative curative, but rather attain their final physical properties through coalescence of the latex particles upon evaporation of solvent or water.